This invention relates to measuring multiple optical properties of biological specimens, such as a population of cells, e.g., blood cells, at high rates of speed using computer controlled instruments that scan the biological specimens.
Examples of such computer controlled instruments include flow cytometers, automated blood cell analyzers and blood cell differential classifiers.
A flow cytometer is an instrument that hydrodynamically focuses a fluid suspension of cells into a single file stream that passes through an examination zone. A focused light beam illuminates the cells in this zone and the instrument measures optical interactions of the light with the cells such as, for example, multiple wavelength absorption, scatter as a function of angle, and fluorescence as a function of either wavelength or polarization. This type of instrument permits the study of living cells in addition to those which have been chemically treated, for example, by staining. Flow cytometry techniques enable certain constituents or structures, particularly those present on the cell surface, to be quantitatively characterized at cell rates of a thousand or more cells per second.
Blood cell analyzers typically consist of a computerized microscope that automatically classifies various types of white blood cells and flags and counts all abnormal cells in a specimen. Using such an automated instrument, the operator can also view the cells manually, stop the analyzer temporarily for making visual morphological observations, or review abnormal cells in greater detail. During the automatic count, the X-Y coordinates of every encountered abnormal blood cell are stored. Therefore, the operator has the option of using a review mode in which abnormal cells are automatically and individually acquired and focused, and can view these cells on a T.V. monitor or through a binocular microscope.
A blood cell differential classifier typically consists of a computer-controlled microscope having a stage that is driven by stepper motors. A light source, such as a xenon arc lamp, illuminates cells and the classifier uses various sensors such as a silicon photodiode array to measure the optical interaction between the cells and the light. All of the cells in a given area are illuminated at the same time.